Floating ball valves are a well known category of ball valves employing top entry and metal seat rings. Such ball valves generally have a valve body, a valve chamber, a ball or a generally spherical member positioned with the valve chamber, and one or two seat members positioned between the ball and the respective ends of the valve chamber. The ball may be rotated from and between an open position in which there is an internal flow path through the ball and through the chamber to a closed position in which the foregoing path is closed.
For the purpose of installing a metal seat, many ball valves must currently undergo an extensive modification process. This is not typical for production valves. This process involves modifying the valve body components to accept custom made and matched components. The re-manufacture of an existing valve thus becomes an expensive and time consuming process which increases the cost and lead time required to produce metal seated products. This has been the norm in the ball valve industry for many years.
Referring to FIG. 1A a prior art standard seat pocket 10 in a ball valve 12 is shown. This standard seat pocket 10 is designed for a polymer seat 14. A raised rim 16 around this seat pocket 10 serves as a fire safe seat when the polymer seat 14 is destroyed in a fire. The single piece polymer seat 14 supports the full pressure load (referenced by arrow 18) of the ball 20 and provides the seal between the body 22 and ball 20. The polymer seat material must therefore be sufficiently resistant to crushing forces to support the ball 20 under pressure while also having low friction characteristics, good chemical compatibility and good sealing ability. Very few materials have all of these desired properties, and that is without the considering the issue of durability of the polymer seat 14 under operational conditions.
‘Metal seat’ technology was developed to address some of the problems faced by polymeric seats, and especially at extreme temperature conditions. Typical ‘metal seat’ technology in use for prior art floating ball valves often requires one to carry out a cumbersome procedure. The procedure involves disassembling the valve, modifying the body components in the area of the seat pocket and then re-assembling the valve with carefully or precision lapped and matched parts.
Referring to FIG. 1B a prior art floating ball valve 30 having custom fitted parts is shown. The valve 30 includes the body 32, ball 34, two seat rings 36a & 36b, a graphite gasket and an energizer spring 38. The body is re-machined in two primary areas 35a & 35b to accept the new style, retrofit seats 36a & 36b. The ball 34 and seat rings 36a & 36b are hand lapped to obtain a precision, leak free fit. The custom fitted parts are installed with back-up components such as the energizer spring 38. The resulting valve 30 is a uni-directional assembly (i.e. the flow direction for the retrofitted valve as represented by arrow 37 cannot be reversed). The modifications and custom fitting of parts adds significantly to the lead time which must be allotted and to the expense of the valve assembly. Such added time and expenses are the current norm in the metal seat floating ball valve industry.
Another problem encountered with prior art floating balls valves results for a lack of available products. Products simply are not available to retrofit or replace the existing components with off-the-shelf ball valve components at a lower cost than custom modifications would allow.